Existing systems for tracking movement tend to have a limited resolving power, that is, the noise associated with the system limits the accuracy with which positions are fixed. The systems generally have a lens which focuses the image of an object on to a light sensitive surface, such as, for example, a surface consisting of an array of charged coupled devices. Each charge coupled device (ccd) is an optical sensor element that reacts to incident light by acquiring an electrical charge. The distribution of charges amongst the elements matches the distribution of light in the image. Each of the elements is sampled, and the image is reproduced, for instance, on a screen, according to the charge distribution.
It is common when tracking movement to monitor specific points on the object under observation by continually fixing the position of the points. From this it is possible to trace not only the path of movement but also the velocity and acceleration components, given that the points are monitored at a known frequency. The points are usually identified either with a source, such as an LED, or a marker capable of reflecting a projected light, for example, a prism or reflective tape. The points are reproduced, in the manner described above, as point images, for instance, on a screen.
In the case of a point source of light, the power with which the location of the point source is resolved will be limited by the fact that the image of the point source will be focused by the lens on to a limited number of elements. The total resolution will consequently be restricted by the individual resolving power of each of the elements on to which the image is focused, and the potential resolving power of the remainder of the elements Is unutilized.